Amnesty International report says rebels may have used chemical weapons and "hell cannon" rockets.

A Syrian rebel group that is laying siege to a Kurdish district in Aleppo may have used chemical weapons, as well as "hell cannon" rockets made from gas canisters, according to a rights group.

Amnesty International said that groups fighting under an alliance known as Jaish al-Fatah have been carrying out indiscriminate attacks on the predominantly Kurdish Sheikh Maqsoud district of the city.

The rebels may have used chemical weapons to target civilian homes, markets and mosques, killing and injuring civilians, Amnesty said on Friday.

Among the weapons used by the groups were unguided projectiles, which cannot be accurately aimed, such as mortars, home-made "Hamim" rockets, and the gas-canister rockets, the report said.

"Hell cannon" projectiles are usually made with cooking-gas canisters, which are packed with explosives and fitted with a fin before being fired from home-made canons.

"Two of the armed groups conducting attacks on Sheikh Maqsoud - Ahrar al-Sham and Army of Islam - have sent representatives to the UN-brokered negotiations on Syria in Geneva, while the others have approved delegates to represent them at the talks," Amnesty said.

"There are around 30,000 civilians living in Sheikh Maqsoud, a district controlled by the Kurdish People’s Protection Unit (YPG) forces, and the area has come under sustained attack from opposition armed groups who control areas to the north, east and west of the district," the report said.

Taj Kordsh, a spokesman for the Syrian Democratic Forces, an alliance which includes the YPG, Jaish al-Thuwar and other Kurdish groups, said there have been several such attacks in recent months.

"These attacks targeted civilians in Sheikh Maqsoud. We have proof that these rebel groups obtained these weapons and used them to target residential areas," Kordsh said.

Amnesty said it had obtained the names of at least 83 civilians, including 30 children, who were killed by attacks in Sheikh Maqsoud between February and April.

One man, Mohamad, lost seven members of his family when his home was struck by an improvised "Hamim" rocket launched by an armed group on 5 April, the group said.

"There are no [military] checkpoints near my house. It is a residential street and there are even people displaced by fighting or who fled air strikes in Aleppo city living on the same street," he told Amnesty.

Saad, a pharmacist, told Amnesty that April 5 was "the bloodiest day the neighbourhood had witnessed". He said that shelling from armed groups went on for nine hours.

Magdalena Mughrabi, Amnesty's Middle East and North Africa deputy director, said that Sheikh Maqsoud was on the brink of a humanitarian crisis.

"It is critical that the Syrian government and armed groups urgently allow unfettered access for humanitarian aid and allow civilians who wish to leave the area to do so," Mughrabi said.

Aleppo ceasefire

On Monday, government forces and rebels in Aleppo agreed to extend their truce for a second time, according to the Syrian army.

The cessation of hostilities was initially to last for two days but was later extended until Tuesday at 00:01 am (21:01 GMT Monday).

Announcing a further extension, the army command said: "The 'regime of silence' in Aleppo and its province has been extended by 48 hours from Tuesday 01:00 am [local time] to midnight on Wednesday."